目的　应用2D/3D图像配准技术进行运动还原以获得正常膝关节韧带的在体稳定性参数。　方法　在生理负重下利用两台C型臂X线机采集8名志愿者健、膝关节屈曲0°、15°、30°、60°和　90°时的两幅相互垂直的X线影像（2D），与由CT重建的三维图像在虚拟X线投射系统进行2D/3D图像配准，还原膝关节不同角度时的股骨和胫骨相对3D位置关系，并通过韧带止点还原的方法对ACL、PCL、　MCL、LCL进行韧带长度分析。　结果　随屈曲角度的增大，ACL长度逐渐缩短，从0°（27.73±1.34）mm至90°（23.34 ±1.48）mm；PCL长度逐渐增加，从0°（26.5±1.65）mm至90°（33.80±1.97） mm；MCL长度逐渐减小，从0°(38.17±1.40)mm至90°时(35.98±1.50) mm。LCL长度同样逐渐减小，从0°(52.56 ±1.64) mm至90°(50.22±1.41) mm。差异均有统计学意义（P＜0.05）。　结论　基于2D/3D图像配准技术可获得正常膝关节生理屈曲过程中韧带长度的变化规律。

Objective　To get the length parameters in vivo of ligaments of healthy knees of Chinese during weight-bearing flexion after motion analysis with the 2D/3D registration technique.　Methods　2 orthogonal X ray images of knees were got under weight-bearing flexion 0°, 15°, 30°, 60°, and 90° in 8 healthy knees of volunteers. These orthogonal images were then imported into virtual fluoroscopic registration system and registered with the three-dimensional models which were reconstructed from CT data with the 2D/3D image registration technology. After 2D/3D image registration, the three-dimensional motions of knees under weight-bearing were showed. Through the bone insertion of ACL/PCL, MCL/LCL, the length parameters of ligaments in vivo were analyzed.　Results　With the flexion angle increased, ACL length gradually shortened, from （27.73±1.34）mm at 0° to （23.34±1.48）mm at 90°s; PCL length increased gradually, from （26.5±1.65） mm at 0° to （33.80±1.97） mm at 90°; MCL length decreased gradually, From（38.17±1.40） mm at 0° to （35.98±1.50） mm at 90°; LCL length gradually reduced, from （52.56±1.64）mm at 0° to （50.22±1.41） mm at 90 °. Differences have statistical significance (P<0.05).　Conclusions　The in vivo ligaments parameters of the healthy knee at different flexion angle can be got through the 2D/3D image registration technique.